We report the high-powered laser modification of
the chemical, physical, and structural properties of the twodimensional
(2D) van der Waals material GaSe. Our results show
that contrary to expectations and previous reports, GaSe at the
periphery of a high-power laser beam does not entirely decompose
into Se and Ga2O3. In contrast, we find unexpectedly that the
Raman signal from GaSe gets amplified around regions where it
was not expected to exist. Atomic force microscopy (AFM),
dielectric force microscopy (DFM), scanning electron microscopy
(SEM), and energy-dispersive X-ray spectroscopy (EDX) results
show that laser irradiation induces the formation of nanoparticles.
Our analyses demonstrate that, except for a fraction of Ga2Se3, these nanoparticles still belong to the GaSe phase but possess
different electrical and optical properties. These changes are evidenced in the increased Raman intensity attributed to the nearresonance
conditions with the Raman excitation laser. The elemental analysis of nanoparticles shows that the relative selenium
content increased to as much as 70% from a 50:50 value in stoichiometric GaSe. This elemental change is related to the formation of
the Ga2Se3 phase identified by Raman spectroscopy at some locations near the edge. Further, we exploit the localized high-power
laser processing of GaSe to induce the formation of Ag−GaSe nanostructures by exposure to a solution of AgNO3. The selective
reaction of AgNO3 with laser-irradiated GaSe gives rise to composite nanostructures that display photocatalytic activity originally
absent in the pristine 2D material. The photocatalytic activity was investigated by the transformation of 4-nitrobenzenethiol to its
amino and dimer forms detected in situ by Raman spectroscopy. This work improves the understanding of light−matter interaction
in layered systems, offering an approach to the formation of laser-induced composites with added functionality.